1. Field of the Invention
The present invention generally relates to a technical field of forming a coated film by landing a discharge liquid discharged through nozzles on a surface of a substrate.
2. Description of the Background Art
A technique using a printer of an ink jet is commonly used to form a coated film on a surface of a substrate.
For example, in FIG. 6, a reference numeral 101 denotes a printer, and a movable arm 112 having a plurality of printing heads 120 is disposed on a table 111.
Each of the printing heads 120 has a plurality of discharge holes 125 (FIG. 7). Piezoelectric elements are disposed inside the printing heads 120. The discharge liquid is discharged through each of the discharge holes 125 by controlling a voltage applied to the piezoelectric elements while the discharge liquid is being fed to the printing head 120 from a tank 116.
A substrate 107 is placed on the table 111. When the discharge liquid is discharged through each printing head 120 while the movable arm 112 is moving, the discharge liquid lands on the surface of the substrate 107 to form a coated film 130 of the discharge liquid. A thin film forms by drying or thermally curing the coated film 130 of the discharge liquid.
Since there are unavailable areas 128 in which discharge holes 125 cannot be formed in both end portions of each of the printing heads 120, in order to dispose the discharge holes 125 consecutively at an equal interval in an identical direction, two adjacent printing heads 120 are disposed forward and rearward of their moving direction so that their end portions are overlapped. Thus, the discharge holes 125 of one printing head 120 disposed rearward in the moving direction pass through a portion of the surface of the substrate 107 where the unavailable area 128 of the other printing head 120, which is disposed forward of the moving direction, passes through.
Further, in order to ensure the overlapping therebetween, a plurality of discharge holes 125 near the end portion of the front printing head 120 and a plurality of the discharge holes 125 near the end portion of the rear printing head 120 are to move along the same pathway and pass above the same position of the substrate.
In order to ensure that the thickness of a coated film 130 formed on the portion through which the overlapped printing heads 120 pass may be equal to the thickness of the coated film formed on a portion through which the discharge holes 125 of one of the front or the rear printing heads 120 passes, and also so that there would not be a portion of the substrate 107 on which no discharge liquid lands, the discharge liquid is discharged only through the discharge holes 125 of either one of the printing heads 120 in the portion where the overlapped discharge holes 125 pass.
In this case, even when the discharge liquids discharged through the respective printing heads 120 land at regular intervals so that the coated film 130 formed with the discharge liquids discharged through the discharge holes 125 of the front printing head 120 may be placed in contact with and adjacent to the coated film 130 formed with the discharge liquids discharged through the discharge holes 125 of the rear printing head 120, there is a problem that there is a possibility that a streak 139 may appear at a portion in which the coated films 130 of the different printing heads 120 are adjacent to each other.
See Japanese Patent Document JP-A 11-138784.